1. Field of the Invention
The present invention relates to electronic siren circuits and more particularly to an improved, compact electronic siren circuit which provides relatively high output power with maximum efficiency.
2. Description of the Prior Art
Prior art electronic siren circuits, such as that disclosed in U.S. Pat. No. 3,051,944 and U.S. Pat. No. Re. 28,745, typically include a voltage controlled variable frequency oscillator which generates a square wave output signal, the square wave having a repetition rate or frequency in the audio frequency range. These circuits further include voltage signal generating circuits which apply a selected one of a plurality of different wave forms to the variable frequency oscillator to produce the desired siren signal. The output signal of the voltage controlled variable frequency oscillator is then applied to a speaker through a suitable power amplifier.
In the majority of applications, the electronic siren is installed in a motor vehicle or similar mobile unit. Consequently, the power and space available to operate and install the siren is limited. For this reason, and due to the need to produce a siren sound having a sufficient volume to be heard above normal ambient sound levels, it is important that the siren circuit produce the desired siren sounds at a relatively high level with maximum efficiency. In this regard, prior art electronic siren circuits exhibit loss of efficiency which results from power losses within the amplifier circuit.